This is a 371 of PCT/1B00/00393 filed Mar. 21, 2000.
The present invention relates to agents and compositions for promoting animal growth, e.g. in underdeveloped humans, and for accelerating tissue repair and regeneration.
Inhibitors of DP-IV
Dipeptidyl peptidase IV (DP-IV, also dipeptidyl aminopeptidase IV, DPP-IV, DAP-IV, EC 3.4.14.5) is a serine peptidase that cleaves the amino-terminal dipeptide from peptides and proteins. It recognises substrates wherein the N-terminal sequence is X-Pro or X-Ala. Inhibitors of DP-IV have been proposed as therapeutic agents for the treatment of inflammatory diseases and AIDS. Generally, the known inhibitors of DP-IV are analogues of the substrate. Examples of DP-IV inhibitors are those disclosed in DD 296 075 A5 (Neubert et al., November 1991), WO91/16339 (Bachovchin et al., October 1991), WO93/08259 (Bachovchin et al, April 1993), WO95/15309 (Jenkins et al., June 1995), WO98/19998 (Villhauer, May 1998), WO99/46272 (Scharpe et al., September 1999) and WO99/61431 (Demuth et al, December 1999). Prodrugs of some of these inhibitors have also been described in WO99/67278 and WO99/67279 (both Demuth et al, December 1999).
The following table sets out general types of DP-IV inhibitor compounds, and specific examples thereof which are amongst those preferred for use in the present invention; it also indicates the patent publications from whose broader range of disclosed compounds these types and examples are drawn. It is emphasised that all DP-IV inhibitors disclosed in the quoted DO and WO specifications can be used in the present invention, and reference is positively directed to these prior specifications for full information on the general and more specific formulae and individual compounds concerned. For example, in the table below the indicated pyrrolidine and thiazolidine rings can be replaced by a wide range of other heterocycles of various ring sizes and/or the indicated aminoacyl moieties can be replaced by a wide range of others, as taught by the indicated publications, to give other DP-IV inhibitors for use in the present invention. 
Actions of Growth Hormone
Growth Hormone (GH, Somatotropin) is secreted by the pituitary in response to a hypothalamic signal in the form of Growth Hormone Releasing Hormone (GHRH). The most abundant isoform of human GH is a 191-residue peptide and GHRH is a 44-residue peptide. GH is a key factor in promoting the normal development of children, and GH deficiency can lead to dwarfism. In adults the importance of GH is less well defined, although plasma levels of GH are similar in adults and children. It is possible that GH plays a role in tissue repair following injury.
The current therapeutic options for GH deficiency include the administration of synthetic GH or of GHRH. However, since both these hormones are peptidic, it is not possible to give them orally. Administration is usually by injection, which can be distressing for the patient (and particularly for children) despite the development of needleless injection systems.
Furthermore, a single injection of GHRH is only an approximation of the pulsatile release of this factor from the hypothalamus. Finally, because both are relatively large peptides, both GHRH and particularly GH are expensive to produce. In consequence, there exists an unmet need for a therapeutic agent that will promote the actions of GH. We have now found that DP-IV inhibitors can increase the concentration of circulating GH.
A first aspect of the present invention is a pharmaceutical composition for the treatment of dwarfism and sub-normal growth (e.g. in children), and for promoting tissue repair (e.g. following injury), which composition is characterized by the inclusion of inhibitor of DP-IV. A second aspect of the present invention is a novel use of inhibitors of DP-IV, namely in the treatment of dwarfism and tissue injury. A third aspect of the invention is an improved protocol for accelerating the growth of children and the regeneration of injured tissue, wherein the subject is administered a composition comprising DP-IV inhibitor.
The use of DP-IV inhibitors in this way presents many advantages over current treatment regimens that involve GH or GHRH. GHRH and particularly GH are large peptides that are either isolated from natural sources (such as animal brain preparations) or prepared in culture using recombinant cells. Isolation from animal sources requires that attention be paid to risk of disease transmission and the presence of antigenic protein contaminants. Recombinant hormones are less likely to transmit human pathogens but are still potentially contaminated with antigenic protein. GHRH can be prepared synthetically, but such a synthesis is expensive and necessitates careful purification of the product. In contrast, DP-IV inhibitors are small molecules that are readily accessible using standard synthetic methods. They are non-antigenic, easy to purify and inexpensive.
A further advantage is that DP-IV inhibitors are in many cases biologically active after oral administration. This is in contrast to GH and GHRH, which must be administered by injection. Hence the use of DP-IV inhibitors leads to a less invasive protocol that is less stressful for the patient.
In a first aspect, the present invention provides a pharmaceutical composition for the treatment of sub-normal development or dwarfism. The composition is particularly effective for the treatment of sub-normal development or dwarfism due to growth hormone deficiency. The invention equally provides a composition for the promotion of tissue regeneration.
These compositions are characterized in that they comprise inhibitor of DP-IV. The compositions may further include such pharmaceutically acceptable excipients as are generally known in the art, such as diluents, carriers, bulking agents, binding agents, dispersants, stabilizers and the like.
In the context of the present invention, a compound is considered to be an inhibitor of DP-IV if it inhibits the action of the enzyme at a concentration of 1 xcexcM. Preferably, such a compound inhibits the action of DP-IV at concentrations below 100 nM and does not inhibit other enzymes at concentrations below 1 xcexcM. The following table sets out general types of DP-IV inhibitor compounds, and specific examples thereof which are amongst those preferred for use in the present invention; it also indicates the patent publications from whose broader range of disclosed compounds these types and examples are drawn. It is emphasised that all DP-IV inhibitors disclosed in the quoted DD and WO specifications can be used in the present invention, and reference is positively directed to these prior specifications for full information on the general and more specific formulae and individual compounds concerned. For example, in the table below the indicated pyrrolidine and thiazolidine rings can be replaced by a wide range of other heterocycles of various ring sizes and/or the indicated aminoacyl moieties can be replaced by a wide range of others, as taught by the indicated publications, to give other DP-IV inhibitors for use in the present invention. 
In a preferred embodiment of the invention, the inhibitor of DP-IV is an amino-acylpyrrolidine nitrile. Particularly preferred are those amino-acyl pyrrolidine nitrites disclosed in WO95/15309 and WO98/19998.
The compositions according to the present invention may be formulated for administration to human subjects by any of the known routes, including oral administration, transmucosal administration (such as buccal, sublingual, intranasal, vaginal and rectal administration), transdermal administration or injection (including intravenous, intramuscular and subcutaneous injection). A preferred route of administration is oral administration. In this case the composition is suitably formulated as a tablet or capsule.
In a second aspect, the present invention comprises a new use for compounds that are known to be inhibitors of DP-IV, which is as therapeutic agents for the treatment of sub-normal development and dwarfism or for the promotion of tissue regeneration.
In a third aspect, the present invention comprises an improved method for the treatment of sub-normal development and dwarfism, particularly that due to growth hormone deficiency, and for the promotion of tissue regeneration, wherein the patient is administered a pharmaceutical composition comprising a therapeutically effective amount of inhibitor of DP-IV. The treatment may involve the use of said composition alone or in conjunction with other agents such as have been described heretofore. The administration may be as a single dose or as divided doses taken at intervals of, for example, 2-6 hours. In a particularly preferred dosing schedule, the composition is given once per day in the evening prior to sleep. The course of treatment might last for a period of a few days or weeks when used to promote tissue regeneration, or for a longer period when used to treat sub-normal development. The responsible physician will determine when a suitable clinical endpoint has been reached, as well as the details of the dosing regimen.